Expression of Ascaris suum malic enzyme in a mutant Escherichia coli allows production of succinic acid from glucose

The malic enzyme gene of Ascaris suum was cloned into the vector pTRC99a in two forms encoding alternative amino-termini. The resulting plasmids, pMEA1 and pMEA2, were introduced into Escherichia coli NZN111, a strain that is unable to grow fermentatively because of inactivation of the genes encoding pyruvate dissimilation. Induction of pMEA1, which encodes the native animoterminus, gave better overexpression of malic enzyme, approx 12-fold compared to uninduced cells. Under the appropriate culture conditions, expression of malic enzyme allowed the fermentative dissimilation of glucose by NZN111. The major fermentation product formed in induced cultures was succinic acid.